Modern mobile operating systems are becoming more and more closed off, and applications are isolated from each other and from the interior of the operating system. At the same time, companies producing operating systems understand and acknowledge certain problems of computer security, such as the threats which a user encounters when web surfing. Understanding the problems of computer security, the makers of operating systems are taking the path of providing to the makers of means for protecting users against cyberthreats a possibility of controlling the downloading of certain rules with which the operating system or a specific application will work. Thus, applications for protecting users against cyberthreats are becoming providers of rules, and these rules are used either by the operating system or by previously installed applications, for example, by means of the web browser plug-in or by means of a plug-in (the “CallDirectory” extension) to the “Telephone” application.
Mobile devices have limited resources such as battery charge, RAM, nonvolatile memory volume, and so on. Problems exist, such as the filtering of web content, which require a large number of rules. On the one hand, the greater the volume of rules loaded onto the mobile device, the higher the probability of blocking web content unwanted by the user, but the more negative the user experience (User eXperience, UX) with the web content filtering system becomes, since the loading of a large volume of rules may slow down the working of the mobile device, and in some instances becomes a cause of crashing of the application for which these rules are loaded. User experience is the perception and responses of a user resulting from the use and/or the previous use of a product, a system, or a service. On the other hand, the more rules, the higher the probability of detection of undesirable content (Detection Rate, DR). A conflict emerges between UX and DR. The more rules, the higher the DR and the worse the UX.
The Apple® company in version 9 of iOS® operating system introduced a new technology of content filtration, making it possible to provide the Safari™ web browser with a set of rules for blocking the display of a site in its entirety or concealing web content (advertising). The set of rules is an application in the form of a plug-in downloadable to Safari (a text file with a list of rules), which may constitute an unlimited or a limited number of rules, such as up to 50,000 content filtering rules. Figures of 50,000 rules are feasible at present, but may change in the course of time. An application may have several such plug-ins, each of which the user needs to turn on manually. The limiting to 50,000 rules was seen by Apple as a solution to the problem of finding a balance between UX and DR in view of the features of the working of the WebKit™ rendering engine component, on the basis of which the Safari browser was developed. Unfortunately, due to limitations of the mobile platform and the browser, Safari simply cannot handle the downloading of a large number of rules, and in some instances they take 10 to 20 minutes to download, and sometimes the downloading results in a crashing of the application and/or Safari. The problem is aggravated because applications have no control over the downloading of the rules, their role is confined to a provider of the rules (“content/rules providers”).
This problem presents itself not only to Apple, but also to applications on other mobile operating systems, including Android®, downloading rules for web content filtering, parental controls, and DNT (Do Not Track).
The existing solutions for minimizing the likelihood of crashing of applications in the process of downloading of rules are aimed at curtailing the number of filtering rules: the fewer the filtering rules, the less the likelihood of a crash and the faster they are downloaded. However, a large number and good quality of filtering rules are needed to maintain a high DR.